X-Windows or VPN

Maybe an How To on X-Windows between Linux (like Fedora 4) and MS-Windows clients (like XP prof) (with a third party client like x-win32)

Or if this is obsolete now (??) mayby a How To on Linux and VPN. Where Linux is the VPN server and serves Linux and Windows clients (with native Microsoft IPSec or Cisco client)

Because Linux would have a strong point for me when I could increase its connectivity towards other produkts. I want to build transparent networks to be able to use the best of different platforms and O.S.